More than a week after this, Peter was sitting on the piazza one evening after tea, reading to his mother, when his friend of the creek expedition came in.
"Here is a card I found, addressed to you, Mrs. Keens," he said. "It must be the one you were hunting for last week, Pete."
She took it in some surprise, failing to observe the color which mounted to Peter's face as he saw it. As she read it, a troubled expression overspread her own.
"Ten days old, this card," she exclaimed. "'Wednesday, the 14th'—what does it mean, Peter?" She passed it to him, and he read as follows:
"July 3.
"My dear Ruth,—I write to give you ample notice of a change in our plans in consequence of Robert's partner desiring to take a trip late in the season, obliging us to go early. So Robert, having finished his business in Canada, is to meet us on Wednesday, the 14th, at Plattsburg. Shall stop for Peter on the evening of the 13th. Please have him ready.
"Katherine."
This was the 13th. Peter stared at his mother in dismay.
"I do not quite understand yet," she said. "Where did you get this card, Philip?"
"I found it just now in the arbor where I have my museum; it had slipped behind a box. You lost it the day we played there, didn't you, Pete?"